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01-01-2015 | Quantitative Methods Special Section

Quantifying ‘problematic’ DIF within an IRT framework: application to a cancer stigma index

Auteurs: Maria Orlando Edelen, Brian D. Stucky, Anita Chandra

Gepubliceerd in: Quality of Life Research | Uitgave 1/2015

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Abstract

Purpose

DIF detection within an IRT framework is highly powerful, often identifying significant DIF that is of little clinical importance. This paper introduces two metrics for IRT DIF evaluation that can discern potentially problematic DIF among items flagged with statistically significant DIF.

Methods

Computation of two DIF metrics—(1) a weighted area between the expected score curves (wABC) and (2) a difference in expected a posteriori scores across item response categories (dEAP)—is described. Their use is demonstrated using data from a 27-item cancer stigma index fielded to four adult samples: (1) Arabic (N = 633) and (2) English speakers (N = 324) residing in Jordan and Egypt, and (3) English (N = 500) and (4) Mandarin speakers (N = 500) residing in China. We used IRTPRO’s DIF module to calculate IRT-based Wald chi-square DIF statistics according to language within each region. After standard p value adjustments for multiple comparisons, we further evaluated DIF impact with wABC and dEAP.

Results

There were a total of twenty statistically significant DIF comparisons after p value adjustment. The wABCs for these items ranged from 0.13 to 0.90. Upon inspection of curves, DIF comparisons with wABCs >0.3 were deemed potentially problematic and were considered further for removal. The dEAP metric was also informative regarding impact of DIF on expected scores, but less consistently useful for narrowing down potentially problematic items.

Conclusions

The calculations of wABC and dEAP function as DIF effect size indicators. Use of these metrics can substantially augment IRT DIF evaluation by discerning truly problematic DIF items among those with statistically significant DIF.
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Metagegevens
Titel
Quantifying ‘problematic’ DIF within an IRT framework: application to a cancer stigma index
Auteurs
Maria Orlando Edelen
Brian D. Stucky
Anita Chandra
Publicatiedatum
01-01-2015
Uitgeverij
Springer International Publishing
Gepubliceerd in
Quality of Life Research / Uitgave 1/2015
Print ISSN: 0962-9343
Elektronisch ISSN: 1573-2649
DOI
https://doi.org/10.1007/s11136-013-0540-4